Assist system and method for aircraft ground operation

ABSTRACT

An aircraft assist system described herein includes an aircraft coupling counterpart attached to a strut of a landing gear of an aircraft, and an assist vehicle. The assist vehicle includes a frame, ground-engaging wheels mounted to the frame, a power source for driving one or more of the ground-engaging wheels, and a vehicle coupling counterpart for engagement with the aircraft coupling counterpart. The aircraft coupling counterpart and the vehicle coupling counterpart define a swivel connection for transferring a propulsive force from the takeoff assist vehicle to the aircraft. The aircraft coupling counterpart is disengageable from the vehicle coupling counterpart by upward movement of the aircraft coupling counterpart relative to the vehicle coupling counterpart.

TECHNICAL FIELD

The application relates generally to aircraft and, more particularly, toground operation of aircraft.

BACKGROUND OF THE ART

The operation of engines of an aircraft for ground movement such astaxiing an aircraft to or from a runway consumes fuel and may berelatively loud. A vehicle often referred to as a “tug” can be utilizedto facilitate the ground movement of aircraft. The tug is a relativelysmall vehicle that couples to the aircraft nose gear so that the vehiclemay tow (i.e., pull) the aircraft. Existing tugs are typically used totaxi the aircraft but are not suitable for propelling the aircraftduring a takeoff phase of operation of the aircraft. Improvement isdesirable.

SUMMARY

In one aspect, there is provided an aircraft takeoff assist systemcomprising:

-   -   an aircraft coupling counterpart attached to a strut of a        landing gear of an aircraft; and    -   a takeoff assist vehicle including:    -   a frame;    -   ground-engaging wheels mounted to the frame;    -   a power source for driving one or more of the ground-engaging        wheels; and    -   a vehicle coupling counterpart for engagement with the aircraft        coupling counterpart, the aircraft coupling counterpart and the        vehicle coupling counterpart defining a swivel connection for        transferring a propulsive force from the takeoff assist vehicle        to the aircraft, the aircraft coupling counterpart being        disengageable from the vehicle coupling counterpart by upward        movement of the aircraft coupling counterpart relative to the        vehicle coupling counterpart.

In another aspect, there is provided an aircraft assist vehiclecomprising:

-   -   a frame;    -   ground-engaging wheels mounted to the frame;    -   a power source for driving one or more of the ground-engaging        wheels;    -   a vehicle coupling counterpart for engagement with an aircraft        coupling counterpart of an aircraft to define a swivel        connection for transferring a propulsive force from the aircraft        assist vehicle to the aircraft, the vehicle coupling counterpart        including an upwardly tapered projection having an electric port        for transferring electric power from the aircraft assist vehicle        to the aircraft.

In a further aspect, there is provided a method of propelling anaircraft with an assist vehicle during a takeoff roll, the methodcomprising:

-   -   with the assist vehicle coupled to a landing gear of the        aircraft and disposed aft of the landing gear, propelling the        aircraft with the assist vehicle by transferring a propulsive        force from the assist vehicle to the aircraft via the landing        gear during the takeoff roll; and    -   after propelling the aircraft with the assist vehicle during the        takeoff roll, decoupling the assist vehicle from the landing        gear of the aircraft.

In a further aspect, there is provided a method of propelling anaircraft on the ground using a two-wheeled unmanned motorcycle. Themethod comprises:

-   -   coupling the two-wheeled unmanned motorcycle to a landing gear        of the aircraft; and    -   propelling the aircraft with the two-wheeled unmanned motorcycle        by transferring a propulsive force from the two-wheeled unmanned        motorcycle to the aircraft via the landing gear when the        aircraft is on ground.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIGS. 1A and 1B are schematic side elevation views of an exemplaryassist vehicle as described herein coupled to an aircraft and assistingwith the ground operation of the aircraft;

FIG. 2 is a schematic representation of an exemplary aircraft assistsystem including the assist vehicle of FIGS. 1A and 1B;

FIG. 3 is a schematic representation of an exemplary controller of theassist vehicle of FIG. 2 ;

FIG. 4 is a flow diagram of a method of propelling an aircraft using anassist vehicle when the aircraft is on the ground;

FIG. 5 is a schematic top plan view of the aircraft of FIGS. 1A and 1Bwith two assist vehicles coupled thereto and assisting with the groundoperation of the aircraft;

FIG. 6A is an exemplary schematic representation of the assist vehiclein a first configuration in preparation for coupling to the aircraft;

FIG. 6B is another exemplary schematic representation of the assistvehicle in a second configuration when the assist vehicle is coupled tothe aircraft; and

FIG. 7 is a schematic top plan view of the assist vehicle of FIGS. 6Aand 6B when coupled to the aircraft.

DETAILED DESCRIPTION

The following description relates to assist vehicles, systems andmethods for assisting with ground operation of aircraft. In someembodiments, the assist vehicles, systems and methods described hereinmay be used to propel an aircraft during taxi and/or takeoff phases ofoperation of the aircraft. The assist vehicles, systems and methodsdescribed herein may be suitable for use with fuel-propelled aircraftand/or for use with electrically-propelled aircraft.

A typical fuel-powered commercial aircraft may use a quantity (e.g., 2to 4 gallons or 7.5 to 15 litres) of fuel per passenger to taxi to thegate, wait at the gate, taxi from the gate to the waiting line and forthe takeoff roll. The energy from that quantity of fuel is used topropel the aircraft, power the aircraft and to condition the passengercabin for example. For an electrically-powered aircraft, such groundoperation may cause additional challenges because the energy required isprovided by onboard batteries. Even though that electric energy isconsumed during the ground operation of the electrically-poweredaircraft, the associated onboard battery weight must be carried for theentire flight. Accordingly, the energy required for normal on-groundoperation may represent a significant weight penalty for theelectrically-powered aircraft.

A typical fuel-powered commercial aircraft may use maximum engine powerduring the take-off roll. At cruise, the fuel-powered aircraft may useapproximately 30% of the maximum engine power. For theelectrically-powered aircraft, the need to produce such high power attakeoff may also influence the size and weight of the batteriesrequired. The battery size and weight required may depend on the type ofbattery(ies) used, the energy density of the battery(ies) and thedischarge efficiency of the battery(ies) at the applicable load. Thebattery weight and size required impacts the payload, range and flighttime of an electrically-powered aircraft.

In some embodiments, the assist vehicles, systems and methods describedherein may be used to limit the fuel consumption of fuel-poweredaircraft and/or limit the energy consumption from the onboardbattery(ies) of electrically-powered aircraft during ground operation.For electrically-powered aircraft, the use of the assist vehicles,systems and methods described herein may reduce or eliminate the needfor onboard battery capacity dedicated for ground operation and/or maypermit more of the onboard battery capacity to be used for flight toextend the range of such aircraft.

The terms “connected”, “coupled” and “attached” used herein may includeboth direct connection, coupling or attachment (in which two elementscontact each other), and indirect connection, coupling or attachment (inwhich at least one additional element is located between the twoelements). The term “substantially” as used herein may be applied tomodify any quantitative representation which could permissibly varywithout resulting in a change in the basic function to which it isrelated.

FIG. 1A is a schematic side elevation view of an exemplary aircraft 10with an exemplary assist vehicle 12 coupled thereto to assist withground operation of aircraft 10. As explained further below, two or moreassist vehicles 12 may be coupled to aircraft 10 to assist with groundoperation of aircraft 10. As described herein, assist vehicle 12 mayassist with powering aircraft 10 and/or propelling aircraft 10 whileaircraft 10 is on ground G. In various situations, ground G mayrepresent an airport apron, taxiway, runway or any surface on whichground movement or stationary operation of aircraft 10 may be conducted.

Aircraft 10 may be any type of manned or unmanned aircraft such as aprivate or commercial passenger aircraft. Aircraft 10 may be afixed-wing aircraft comprising one or more electric aircraft motors 14(referred hereinafter in the singular) driving one or more propellers16. Aircraft 10 may be electrically-powered but it is understood thatassist vehicle 12 may also be used with fuel-powered aircraft (e.g.,propelled by gas turbine engines). Aircraft 10 may include one or moreaircraft batteries 18 (referred hereinafter in the singular) operativelyconnected to supply electric power to aircraft motor 14 and also one ormore other aircraft systems 20. Aircraft systems 20 may include anenvironmental control system for conditioning a passenger cabin ofaircraft 10, an anti-icing system, a lighting system, a hydraulicsystem, avionics, lavatory operation and/or other electric load(s) thatmay be onboard aircraft 10.

Assist vehicle 12 may be coupled to aircraft 10 so that a propulsiveforce may be transferred from assist vehicle 12 to aircraft 10. Assistvehicle 12 may be suitable to propel aircraft 10 in the forward and/oraft directions as indicated in FIG. 1A and may also be suitable topropel aircraft 10 along a curved trajectory. In various embodiments,assist vehicle 12 may be configured to be coupled to main landing gear22, to nose landing gear 24, and/or to another suitable couplinglocation on aircraft 10. In some embodiments, assist vehicle 12 may beconfigured to be coupled to strut 26 of main landing gear 22 so that thepropulsive force(s) may be transferred to aircraft 10 via strut 26.

The coupling of aircraft 10 with assist vehicle 12 may be achieved viasuitable coupling counterparts between trailing link 28 of aircraft 10and push link 30 of assist vehicle 12. Trailing link 28 may be attached(e.g., fastened or otherwise secured) to strut 26. Trailing link 28 mayextend aft (rearwardly) of strut 26. Push (and/or pull) link 30 may beattached to assist vehicle 12. Push link 30 may be disposed in a frontregion of assist vehicle 12. The coupling between trailing link 28 andpush link 30 may provide a swivel connection suitable for transferring a(e.g., pushing or pulling) propulsive force between aircraft 10 andassist vehicle 12 while also permitting a swivelling movement betweentrailing link 28 and push link 30. The configuration of trailing link 28and push link 30 may cause the swivel connection to be disposed aft ofstrut 26 and also permit assist vehicle 12 to be positioned aft of strut26 and of main landing gear 22 when assist vehicle 12 is coupled toaircraft 10 and optionally propelling aircraft 10 when aircraft 10 is onground G. The position of assist vehicle 12 aft of main landing gear 22may facilitate the use of assist vehicle 12 for propelling aircraft 10during takeoff of aircraft 10 so that assist vehicle 12 may be leftbehind aircraft 10 and clear of the path of aircraft 10 when aircraft 10takes flight as shown in FIG. 1B.

When assist vehicle 12 is coupled to aircraft 10 and optionallypropelling aircraft 10, electric power may be transferred from assistvehicle 12 to aircraft 10 to power one or more aircraft systems 20and/or aircraft motor 14. This may permit aircraft 10 to be electricallypowered via assist vehicle 12 in order to reduce or eliminate the needfor aircraft 10 to consume electric power from onboard aircraft battery18 during ground operation. When aircraft 10 is propelled forward byassist vehicle 12 during the takeoff roll for example, aircraft motor 14may also be driven so that aircraft 10 may also be propelled viapropeller 16. In this scenario, assist vehicle 12 may be used tosupplement the propulsion provided via aircraft motor 14. In variousembodiments, electric power transferred from assist vehicle 12 and/orfrom onboard aircraft battery 18 may be used to drive aircraft motor 14and accelerate aircraft 10 to the rotation speed during the takeoffroll.

When assist vehicle 12 is coupled to aircraft 10, data may betransferred between assist vehicle 12 and one or more devices 32 ofaircraft 10 via wired and/or wireless connection(s). Such aircraftdevices 32 may include brake/rudder pedals, a tiller, and/or a thrust(e.g., throttle) lever for example. In some embodiments, such datareceived at assist vehicle 12 may represent pilot commands to brake,steer and/or accelerate aircraft 10. Such data may be used to controlthe operation of assist vehicle 12 and cause assist vehicle 12 to reactin accordance with pilot commands.

As explained below, assist vehicle 12 may be configured as an unmannedself-driving (e.g., autonomous) two-wheeled motorcycle including frontwheel 34 and rear wheel 36 arranged in tandem. Push link 30 may bedisposed in tandem with front wheel 34 and rear wheel 36. Front wheel 34may be disposed between push link 30 and rear wheel 36. It is understoodthat assist vehicle 12 may have other configurations than those shownherein. For example, assist vehicle 12 may be a three-wheeled or afour-wheeled vehicle in some embodiments.

FIG. 1B is a schematic side elevation view of aircraft 10 taking flightafter being propelled by assist vehicle 12 during the takeoff rollduring which the aircraft 10 is accelerated from a standstill to anairspeed that provides sufficient lift for aircraft 10 to becomeairborne. The scenario illustrated in FIG. 1A may represent thepropelling of aircraft 10 using assist vehicle 12 during the takeoffroll. The moment shown in FIG. 1B may be shortly after lift-off when thewings of aircraft 10 are lifting the weight of aircraft 10 off of groundG. In some situations, the lift-off may be accompanied by the pilot ofaircraft 10 causing rotation of aircraft 10 to bring the nose ofaircraft 10 upward and increase the angle of attack of aircraft 10. Insome embodiments, assist vehicle 12 may be used to propel aircraft 10until the rotation speed of aircraft 10 has been reached. For some(e.g., earlier) portion(s) of the takeoff roll, a majority or all of thepropulsive force required to accelerate aircraft 10 may be supplied byone or more assist vehicles 12. For some (e.g., later) portion(s) of thetakeoff roll, aircraft motor 14 of aircraft 10 may also operate togenerate some of the propulsive force so that when the propulsion ofaircraft 10 via assist vehicle 12 is ceased at or around lift-off forexample, the propulsion of aircraft 10 may continue and be taken over byaircraft motor 14 and propeller(s) 16.

The coupling mechanism used to coupled assist vehicle 12 to aircraft 10may be configured to remain in a force-transmitting engagement whenaircraft 10 is on ground G and being propelled by assist vehicle 12, andautomatically become disengaged after the takeoff roll. In other words,the coupling mechanism may, in some embodiments, be configured toself-disengage at the appropriate time at or near the end of the takeoffroll. For example, the coupling mechanism may be configured to becomeautomatically disengaged by upward movement of trailing link 28 ofaircraft 10 relative to push link 30 of assist vehicle 12 as explainedbelow.

FIG. 2 is a schematic representation of an exemplary aircraft assistsystem 38 including assist vehicle 12. In some embodiments, aircraftassist system 38 may include two assist vehicles 12. In variousembodiments, assist vehicle 12 may be fuel-powered (e.g., include aninternal combustion engine), electrically powered via one or morevehicle battery(ies) 40 (referred hereinafter in the singular) and oneor more electric vehicle motors 42, or may include a hybrid (e.g., fueland electric) powertrain. In embodiments where assist vehicle 12 iselectrically powered as illustrated in FIG. 2 , the powertrain of assistvehicle 12 may include battery 40 and one or more electric vehiclemotors 42 drivingly coupled to front wheel 34 and/or to rear wheel 36.In some embodiments, vehicle motor(s) 42 may include one or morein-wheel electric motors operatively coupled to drive front wheel 34and/or rear wheel 36 to propel assist vehicle 12.

In some embodiments, battery 40 may serve as a power source forpropelling assist vehicle 12 and also for supplying electric power toaircraft 10. In some embodiments, battery 40 may include a lithium-ionor other suitable type of battery(ies). Various aspects of assistvehicle 12 may be sized based on the duty cycle of assist vehicle 12 andbased on the specifications of aircraft 10 that assist vehicle 12 willbe assisting. In some embodiments and depending on the type ofbattery(ies) used, battery 40 may be sized to have a mass of 40 to 80kg/passenger of aircraft 10.

In some embodiments, assist vehicle 12 may be configured to provide 100%of the normal acceleration of aircraft 10 obtainable from aircraft motor14 during at least part of the takeoff roll which may last about 15seconds. In some embodiments, assist vehicle 12 may be configured toalso provide electric power to aircraft motor 14. The combinedpropulsion of aircraft 10 via assist vehicle 12 and via aircraft motor14 may provide an increased acceleration of aircraft 10 when using ashort runway or having a heavy payload.

The operation of vehicle motor(s) 42 and the delivery of electric powerfrom battery 40 to vehicle motor(s) 42 may be controlled by controller44 via a suitable power electronics module (PEM) 46 including electronicswitches to perform a suitable power conversion function and providevehicle motor(s) 42 with electric power having the desired voltage,current, waveform, etc. to implement the desired propulsion behaviourand performance of assist vehicle 12 when assist vehicle 12 is coupledto aircraft 10 or when assist vehicle 12 is in transit to/from aircraft10 such as, for example, between aircraft 10 and base station 48.

The powertrain of assist vehicle 12 may also include flywheel 50 thatmay serve to store kinetic energy. In embodiments where assist vehicle12 is a two-wheeled vehicle, flywheel 50 may also serve an additionalfunction of providing dynamic stability in helping keep assist vehicle12 in the upright orientation during use. In some situations, flywheel50 may be driven by vehicle motor(s) 42 to store energy in preparationfor propelling aircraft 10 for example. In situations where assistvehicle 12 must rapidly accelerate aircraft 10 during the takeoff rolefor example, energy stored in flywheel 50 may be used to supplement thepropulsive force delivered from vehicle motor(s) 42 via front wheel 34and/or rear wheel 36. The energy stored in flywheel 50 may betransferred to front wheel 34 and/or to rear wheel 36 via one or moresuitable clutches (not shown) for example. In some situations wherebraking of assist vehicle 12 is required, recuperative braking may beconducted by transferring energy from front wheel 34 and/or from rearwheel 36 to flywheel 50 via the same or other clutch(es). Battery 40 andflywheel 50 may be disposed between front wheel 34 and rear wheel 36.

In various embodiments of assist vehicle 12, front wheel 34 and/or rearwheel 36 may be steerable via one or more steering actuators 52(referred hereinafter in the singular). Steering actuator 52 may includean electric actuator or a hydraulic actuator for example. Steeringactuator 52 may be operatively connected to be controllable viacontroller 44.

In some embodiments, assist vehicle 12 may include a variable-heightsuspension to facilitate coupling and uncoupling of assist vehicle 12 toand from aircraft 10 as described further below. Assist vehicle 12 mayinclude one or more kneeling actuators 54 (referred hereinafter in thesingular) operatively connected to front wheel 34 and/or to rear wheel36 to permit a frame of assist vehicle 12 to be raised and loweredrelative to ground G. Kneeling actuator 54 may include an electricactuator or a hydraulic actuator for example. Kneeling actuator 54 maybe operatively connected to be controllable via controller 44.

In some embodiments, assist vehicle 12 may be unmanned and self-driving(e.g., partially or entirely autonomous). Assist vehicle 12 may includenavigation system 56 operatively connected to controller 44 to guide themovement of assist vehicle 12 during one or more portions of its dutycycle. Navigation system 56 may include a position data feedback systemwhich may be global positioning system (GPS)-based and/orgyroscope-based. Real-time position data of assist vehicle 12 may beused to control movement of assist vehicle 12 when not coupled toaircraft 10. Navigation system 56 may permit navigation of the airfieldusing optical markers, magnetic markers, beacons, GPS or a combinationof these methods. The approach of assist vehicle 12 to aircraft 10 andmain landing gear 22 in preparation for coupling may be guided by one ormore proximity sensor(s) 58 disposed on assist vehicle 12 and one ormore cooperating targets 60 disposed on trailing link 28, on mainlanding gear 22 or elsewhere on aircraft 10. In some embodiments, theapproach of assist vehicle 12 to aircraft 10 and main landing gear 22 inpreparation for coupling may be guided through the use of radar-, laser-or ultrasound-based distance measurement systems or a combination ofdifferent measurement systems. Alternatively or in addition, the use ofimage recognition may also be used to guide the movement and operationof assist vehicle 12 and facilitate coupling to aircraft 10.

During operation, assist vehicle 12 may be in wireless communicationwith base station 48 and/or with aircraft 10 to permit commands to bewirelessly transmitted to assist vehicle 12 and/or permit the operationand status of assist vehicle 12 may be monitored and/or controlledremotely by computer and/or by a human operator for example. During adeparture of aircraft 10, the duty cycle of assist vehicle 12 mayinclude moving assist vehicle 12 from base station 48 to aircraft 10,coupling assist vehicle 12 to aircraft 10, taxiing aircraft 10 from agate or hanger to the brake-release point of an active runway,propelling aircraft 10 during the takeoff roll, decoupling assistvehicle 12 from aircraft 10, and returning assist vehicle 12 to basestation 48. During an arrival of aircraft 10, the duty cycle of assistvehicle 12 may include moving assist vehicle 12 from base station 48 toaircraft 10 when aircraft 10 has finished the landing roll, couplingassist vehicle 12 to aircraft 10, taxiing aircraft 10 to the gate orhanger, decoupling assist vehicle 12 from aircraft 10 and returningassist vehicle 12 to base station 48. In some embodiments, base station48 may also include a charging facility for recharging battery 40 ofassist vehicle 12, and/or may include a re-fueling station.

The coupling of assist vehicle 12 to aircraft 10 may be achieved via theengagement of cooperating vehicle coupling counterpart 62 of assistvehicle 12 and aircraft coupling counterpart 64 of aircraft 10. Invarious embodiments, vehicle coupling counterpart 62 and aircraftcoupling counterpart 64 may provide mechanical engagement and optionallyalso electric, pneumatic and/or data transfer engagement. In someembodiments, vehicle coupling counterpart 62 and aircraft couplingcounterpart 64 may, when engaged with each other, be configured todefine a swivel connection having swivel axis S. The swivel connectionmay also be configured to transfer the propulsive force between assistvehicle 12 and aircraft 10. In some embodiments, the coupling mechanismmay include suitable (e.g., mechanical, electro-mechanical,electro-pneumatic and/or electro-magnetic) linkage(s).

In some embodiments, vehicle coupling counterpart 62 and aircraftcoupling counterpart 64 may be engaged and disengaged by way of relativevertical movement between vehicle coupling counterpart 62 and aircraftcoupling counterpart 64. For example, aircraft coupling counterpart 64may be disengaged from vehicle coupling counterpart 62 by upwardmovement of aircraft coupling counterpart 64 relative to vehiclecoupling counterpart 62. Such disengagement mechanism may facilitateautomated and self-decoupling of assist vehicle 12 from aircraft 10following the takeoff roll.

In some embodiments, aircraft coupling counterpart 64 may include socket66 with a downwardly facing opening. Socket 66 may integrated with orotherwise attached to trailing link 28. Vehicle coupling counterpart 62may include projection 68 configured to be received into socket 66 andmatingly engaged with socket 66. Projection 68 may be integrated with orotherwise attached to push link 30. Alternatively, in some embodiments,a socket with an upwardly facing opening could instead be integratedwith or otherwise attached to push link 30, and a cooperating projectioncould instead be integrated with or otherwise attached to trailing link28. Socket 66 and projection 68 may be made from metallic or othersuitable structural material(s).

Other types of coupling mechanisms may be suitable. For example, variousshapes of socket 66 and of projection 68 are envisioned. In someembodiments, projection 68 and/or socket 66 may be upwardly tapered. Insome embodiments, the outer shape of projection 68 and/or the innershape of socket 66 may be axisymmetric about swivel axis S defined whenprojection 68 is received in socket 66. In some embodiments, projection68 and/or socket 66 may be at least partially conical in shape. Forexample, projection 68 and/or socket 66 may have a generallyfrustoconical shape. For example, projection 68 and/or socket 66 mayhave the general shape of a frustum. In some embodiments, projection 68and/or socket 66 may be at least partially cylindrical and/or at leastpartially spherical in shape.

Projection 68 and socket 66 may optionally cooperatively define anelectric power transfer interface between assist vehicle 12 and aircraft10 to permit electric power to be transferred from assist vehicle 12 toaircraft 10. The electric power interface may be defined by way ofaircraft electric port 70 disposed in socket 66, and cooperating vehicleelectric port 72 disposed on projection 68. In some embodiments,aircraft electric port 70 and vehicle electric port 72 may includeelectric contact surfaces that are (e.g., ring-shaped or otherwise)configured to accommodate some swivelling movement between socket 66 andprojection 68.

Projection 68 and socket 66 may optionally cooperatively define a datatransfer interface between assist vehicle 12 and aircraft 10 to permitcommands from aircraft device(s) 32 to be received by assist vehicle 12and/or other (e.g., aircraft-mission-relevant) data transfer betweenassist vehicle 12 and aircraft 10. The data transfer interface may bedefined by way of aircraft data port 74 disposed in socket 66, andcooperating vehicle data port 76 disposed on projection 68. In someembodiments, aircraft data port 74 and vehicle data port 76 may includecontact surfaces that are (e.g., ring-shaped or otherwise) configured toaccommodate some swivelling movement between socket 66 and projection68. Aircraft data port 74 and vehicle data port 76 may provide a wiredconnection for data transfer. Alternatively or in addition, datatransfer between assist vehicle 12 and aircraft 10 may be conductedwirelessly.

Projection 68 and socket 66 may optionally cooperatively define apneumatic interface between assist vehicle 12 and aircraft 10 to permitpressurized air to be transferred from assist vehicle 12 to aircraft 10.In some embodiments, assist vehicle 12 may include a compressor, tank orother source of pressurized air that may be used to supply one or morepneumatic loads onboard of aircraft 10 when assist vehicle 12 is coupledto aircraft 10.

FIG. 3 is an exemplary schematic representation of controller 44 ofassist vehicle 12. Controller 44 may include one or more data processors78 (referred hereinafter as “processor 78”) and non-transitorymachine-readable memory 80. Controller 44 may be configured to controlvarious aspects of operation of assist vehicle 12. Controller 44 mayreceive input(s) 82, perform one or more procedures or steps defined byinstructions 84 stored in memory 80 and executable by processor 78 togenerate output(s) 86. Controller 44 may include multiple controllersonboard assist vehicle 12, and/or some controllers may be locatedremotely of assist vehicle 12.

Controller 44 may carry out additional functions than those describedherein. Processor 78 may include any suitable device(s) configured tocause a series of steps to be performed by controller 44 so as toimplement a computer-implemented process such that instructions 84, whenexecuted by controller 44 or other programmable apparatus, may cause thefunctions/acts specified in the methods described herein to be executed.Processor 78 may include, for example, any type of general-purposemicroprocessor or microcontroller, a digital signal processing (DSP)processor, an integrated circuit, a field programmable gate array(FPGA), a reconfigurable processor, other suitably programmed orprogrammable logic circuits, or any combination thereof.

Memory 80 may include any suitable machine-readable storage medium.Memory 80 may include non-transitory computer readable storage mediumsuch as, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,or device, or any suitable combination of the foregoing. Memory 80 mayinclude a suitable combination of any type of machine-readable memorythat is located either internally or externally to controller 44. Memory80 may include any storage means (e.g. devices) suitable for retrievablystoring machine-readable instructions 84 executable by processor 78.

Various aspects of the present disclosure may be embodied as systems,devices, methods and/or computer program products. Accordingly, aspectsof the present disclosure may take the form of an entirely hardwareembodiment, an entirely software embodiment or an embodiment combiningsoftware and hardware aspects. Furthermore, aspects of the presentdisclosure may take the form of a computer program product embodied inone or more non-transitory computer readable medium(ia) (e.g., memory80) having computer readable program code (e.g., instructions 84)embodied thereon. Computer program code for carrying out operations foraspects of the present disclosure in accordance with instructions 84 maybe written in any combination of one or more programming languages. Suchprogram code may be executed entirely or in part by controller 44 orother data processing device(s). It is understood that, based on thepresent disclosure, one skilled in the relevant arts could readily writecomputer program code for implementing the methods described andillustrated herein.

FIG. 4 is a flow diagram of an exemplary method 1000 of assisting withground operation and/or propelling of aircraft 10. Method 1000 may beperformed using assist vehicle 12 or other assist vehicle when aircraft10 is on ground G. Machine-readable instructions 84 may be configured tocause controller 44 to cause actions useful in performing at least partof method 1000. Aspects of method 1000 may be combined with otheractions or aspects of other methods described herein. Aspects ofaircraft assist system 38 and of assist vehicle 12 described herein mayalso be incorporated into method 1000. In various embodiments, method1000 may include:

-   -   coupling assist vehicle 12 to main landing gear 22 of aircraft        10 (block 1002); and    -   propelling aircraft 10 with assist vehicle 12 (block 1004).

Aspects of method 1000 are described below in reference to other figuresprovided herein. As shown in FIG. 1A, assist vehicle 12 may be coupledto main landing gear 22 so that assist vehicle 12 is disposed aft ofmain landing gear 22. Propelling of aircraft 10 with assist vehicle 12may be performed by transferring a propulsive (e.g., pushing or pulling)force from assist vehicle 12 to aircraft 10 via main landing gear 22.Propelling of aircraft 10 with assist vehicle 12 may be performed duringa taxi and/or during a takeoff phase of operation (e.g., during thetakeoff roll) of aircraft 10. After propelling aircraft 10 with theassist vehicle 12, assist vehicle 12 may be decoupled from main landinggear 22 of aircraft 10. The location of assist vehicle 12 behind mainlanding gear 22 may allow assist vehicle 12 to be left behind aircraft10 and reduce the risk of assist vehicle 12 interfering with the forwardmovement of aircraft 10 in the event of a malfunction for example. Partof the duty cycle of assist vehicle 12 may include autonomously drivingfrom base station 48 to aircraft 10 before propelling aircraft 10, andautonomously driving back to base station 48 after propelling aircraft10.

FIG. 5 is a schematic top plan view of aircraft 10 with two assistvehicles 12A and 12B (also referred generally herein as “assist vehicle12”) coupled thereto and assisting with the ground operation, and/orassisting with the propulsion of aircraft 10 during the takeoff rolland/or during taxi. Assist vehicles 12A, 12B may each be configured as arelatively fast two-wheeled unmanned motorcycle. In some embodimentsassist vehicles 12A, 12B may be used to propel aircraft 10 forward andrearward. Differential traction between assist vehicles 12A, 12B mayalso cause turning of aircraft 10 to allow aircraft 10 to follow acurved trajectory or to be reoriented for example.

First assist vehicle 12A may be coupled to first strut 26A of mainlanding gear 22 and second assist vehicle 12B may be coupled to secondstrut 26B of main landing gear 22 as shown in FIG. 5 . In thisconfiguration, respective propulsive forces may be transferred toaircraft 10 by respective first and second assist vehicles 12A, 12B viarespective first and second struts 26A, 26B. As explained above,electric power may be transferred from one or from both first and secondassist vehicles 12A, 12B to aircraft motor 14 and/or other aircraftsystems 20. Data from aircraft device(s) 32 may also be transferred toone or to both first and second assist vehicles 12A, 12B so that firstand/or second assist vehicles 12A, 12B may be controlled according topilot commands. After propelling aircraft 10 with first and secondassist vehicles 12A, 12B during the takeoff roll, or after other type ofaircraft assistance provided, first and second assist vehicles 12A, 12Bmay be decoupled from their respective first and second struts 26A, 26B.

FIG. 6A is an exemplary schematic representation of assist vehicle 12 ina first configuration in preparation for coupling to aircraft 10. Invarious embodiments, vehicle coupling counterpart 62 and aircraftcoupling counterparts 64 may be configured to be engaged manually by ahuman operator, or may be configured to be engaged autonomously. Forexample, assist vehicle 12 may be configured to cause vertical movementof projection 68 by way of push link 30 being articulated andcontrollably movable relative to frame 88 of assist vehicle 12. In theembodiment shown in FIG. 6A, assist vehicle 12 may have a variableheight suspension configured to cause kneeling of assist vehicle 12 inorder to lower projection 68 below socket 66 and then raise projection68 into socket 66 to cause engagement of projection 68 with socket 66.Kneeling of assist vehicle 12 may be achieved via kneeling actuator 54adjusting the position of rear wheel 36 relative to frame 88. Forexample, moving (e.g., deploying) rear wheel 36 to cause a rear portionof frame 88 to be raised may cause projection 68 to be lowered to aheight permitting projection 68 to be advanced under socket 66 oftrailing link 28. Once projection 68 is aligned with socket 66, rearwheel 36 may be moved in the opposite direction (e.g., retracted) tocause the rear portion of frame 88 to be lowered and consequentlyprojection 68 to become engaged with socket 66 as shown in FIG. 6B. Inother words, the actuation of kneeling actuator 54 and the resultingvariable position of rear wheel 36 may cause frame 88 to pivot as alever about front wheel 34 serving as a fulcrum.

Assist vehicle 12 may include frame 88 to which front wheel 34 and rearwheel 36 may be mounted. Front wheel 34 may be steerable via steeringactuator 52 shown in FIG. 2 . In some embodiments, assist vehicle 12 mayinclude steering damper 90 sometimes called a steering stabilizer.Steering damper 90 may hinder or prevent undesirable and uncontrolledsteering movements or oscillations known as “wobble” in motorcycling.Steering damper 90 may allow steering during autonomous operation andmay also help hold front wheel 34 straight when assist vehicle 12 ispropelling aircraft 10 at relatively high speed for example.

Push link 30 may be mounted in cantilevered manner in a front portion ofassist vehicle 12 and forward of front wheel 34. In other words, frontwheel 34 may be disposed between projection 68 and rear wheel 36. Pushlink 30 may be movably attached to frame 88 of assist vehicle 12 inorder to permit some relative movement between projection 68 and frame88 during operation. In some embodiments, push link 30 may be attachedto control link 92 at first connection 94A. Frame 88 and control link 92may be made from metallic material(s) (e.g., aluminum, steel) or othersuitable structural material(s). Frame 88 and control link 92 may have arelatively rigid construction.

First connection 94A may permit relative (e.g., rotational, pivotal)movement between push link 30 and control link 92. In some embodiments,first connection 94A may include a knuckle joint, hinge joint, a balland socket (i.e., spheroid) joint, or a elastomeric (e.g., rubber)bushing for example. Push link 30 may also be supported by frame 88 viapad 96 which may provide some damping while allowing some relativelysmall omnidirectional movement of push link 30 and projection 68relative to frame 88. Pad 96 may be made of an elastomeric (e.g.,rubber) or other vibration damping material.

Control link 92 may be connected to a top end of steering shaft 98 offront wheel 34 at second connection 94B. Steering shaft 98 may bepivotable relative to control link 92. Second connection 94B may be acylindrical joint or a ball and socket joint. Control link 92 may alsobe connected to frame 88 at third connection 94C. Third connection 94Cmay be axially disposed between front wheel 34 and rear wheel 36. Thirdconnection 94C may be a substantially rigid connection between controllink 92 and frame 88. In various embodiments, control link 92 may befastened or otherwise secured to frame 88 at third connection 94C.

In some embodiments, all or part of vehicle battery 40 and/or all orpart of flywheel 50 may be disposed between front wheel 34 and rearwheel 36.

FIG. 6B is another exemplary schematic representation of assist vehicle12 in a second configuration where assist vehicle 12 is coupled toaircraft 10. In this configuration, kneeling actuator 54 has caused rearwheel 36 to be retracted and consequently caused projection 68 to beraised and become received into and engaged with socket 66. In somesituations, rear wheel 36 may be retracted until a relatively small loadis carried by rear wheel 36. By way of front wheel 34 serving as afulcrum, this loading may cause some of the weight of aircraft 10 to betransferred from trailing link 28 via socket 66 and projection 68 topush link 30, to frame 88 and consequently to front wheel 34. Thisloading may cause front wheel 34 to be loaded with some weight of assistvehicle 12 and some weight of aircraft 10 and may promote good tractionof front wheel 34 with ground G when front wheel 34 is driven to propelaircraft 10. The positional adjustment of rear wheel 36 relative toframe 88 causing weight of aircraft 10 to push downwardly on front wheel34 may also promote secure engagement of projection 68 with socket 66.When projection 68 is engaged with socket 66, assist vehicle 12 may bepivot relative to aircraft 10 about swivel axis S.

FIG. 7 is a schematic top plan view of assist vehicle 12 of FIG. 5 whencoupled to first strut 26A of aircraft 10 during a turning maneuver ofaircraft 10. When aircraft is propelled by assist vehicles 12A and 12B,the turning maneuver may be initiated by the pilot and caused by theturning of nose landing gear 24 and/or a differential application ofaircraft brakes. In some embodiments, the two-wheeled arrangement ofassist vehicle 12A may be suitable for accommodating and react tosteering of aircraft 10. The two-wheeled construction of assist vehicle12A may be relatively simple and light relative to a three-wheeled orfour-wheeled alternative. Also, by virtue of the two wheels beingarranged in tandem, this arrangement may promote self-alignment ofassist vehicle 12 with aircraft 10 at various phases of ground operationincluding the takeoff roll.

In reference to FIGS. 6A and 6B, control link 92 may help dynamicallystabilize assist vehicle 12 and hinder uncontrolled shimmy. When noselanding gear 24 steers one way and causes aircraft 10 to rotate aboutpoint O for example, the whole aircraft 10 may start yawing in thatdirection and cause trailing link 28 to wag in the opposite direction asindicated by arrow A1. This may cause push link 30 to tilt due to thelateral moment applied by socket 66. This may make a forward part ofcontrol link 92 also wag with trailing link 28 as indicated by arrow A2at the location of first connection 94A. Control link 92 may then becaused to pivot about second connection 94B as indicated by arrow A3.Such behaviour of control link 92 may consequently induce an oppositelateral motion of frame 88 as indicated by arrow A4 at third connection94C. The lateral motion of frame 88 may force rear wheel 36 to becomeout of alignment with (e.g., angled relative to) front wheel 34. Thismay consequently induce an automatic anticipative steering motion ofassist vehicle 12 causing assist vehicle 12 to enter a circular pathbehind aircraft 10 in response to the steering of aircraft 10. In someembodiments, the behaviour of assist vehicle 12 in response to steeringof aircraft 10 may be assisted by steering actuator 52 based on one ormore pilot commands indicative of steering of nose landing gear 24and/or a differential application of aircraft brakes communicated fromaircraft 10 to assist vehicle 12 as described above for example.

In reference to the figures herein, in one aspect, the disclosuredescribes an aircraft takeoff assist system 38 comprising: an aircraftcoupling counterpart 64 attached to a strut 26 of a landing gear 22 ofan aircraft 10; and a takeoff assist vehicle 12 including: a frame 88;ground-engaging wheels 34, 36 mounted to the frame 88; a power source(e.g., vehicle battery 40, vehicle motor 42) for driving one or more ofthe ground-engaging wheels 34, 36; and a vehicle coupling counterpart 62for engagement with the aircraft coupling counterpart 64, the aircraftcoupling counterpart 64 and the vehicle coupling counterpart 62 defininga swivel connection for transferring a propulsive force from the takeoffassist vehicle 12 to the aircraft 10, the aircraft coupling counterpart64 being disengageable from the vehicle coupling counterpart 62 byupward movement of the aircraft coupling counterpart 64 relative to thevehicle coupling counterpart 62.

The takeoff assist vehicle 12 may be an unmanned two-wheeled motorcycle.

The swivel connection may be disposed aft of the strut 26 of the landinggear 22.

The landing gear 22 may be a main landing gear 22 of the aircraft 10.

In some embodiments of the aircraft takeoff assist system 38: thetakeoff assist vehicle 12 may be a first takeoff assist vehicle 12A; theaircraft coupling counterpart 64 may be a first aircraft couplingcounterpart 64; the strut 26 may be a first strut 26A; the landing gear22 may be a main landing gear 22 of the aircraft 10; and the aircrafttakeoff assist system 38 may include a second takeoff assist vehicle 12Bfor engagement with a second strut 26B of the main landing gear 22.

The first and second takeoff assist vehicles 12A, 12B may be unmannedtwo-wheeled motorcycles.

In some embodiments of the aircraft takeoff assist system 38: theaircraft coupling counterpart 64 may include a socket 66 with adownwardly facing opening; and the vehicle coupling counterpart 62 mayinclude a projection 68 configured to be received in the socket 66.

The projection 68 may be upwardly tapered.

The projection 68 may have a conical shape.

The projection 68 and the socket 66 may cooperatively define an electricpower transfer interface between the takeoff assist vehicle 12 and theaircraft 10.

The projection 68 and the socket 66 may cooperatively define a datatransfer interface between the takeoff assist vehicle 12 and theaircraft 10.

The aircraft coupling counterpart 64 may be disposed aft of the strut 26and may be attached to the strut 26 via a trailing link 28.

In some embodiments of the aircraft takeoff assist system 38: thetakeoff assist vehicle 12 may be an unmanned two-wheeled vehicle 12having a first ground-engaging wheel 34 and a second ground-engagingwheel 36 arranged in tandem; and the vehicle coupling counterpart 62 maybe disposed in tandem with the first and second ground-engaging wheels34, 36 of the takeoff assist vehicle 12.

In some embodiments of the aircraft takeoff assist system 38: the firstground-engaging wheel 34 is disposed between the vehicle couplingcounterpart 62 and the second ground-engaging wheel 36; and the takeoffassist vehicle 12 may include an electric motor 42 operatively connectedto drive the first ground-engaging wheel 34.

The takeoff assist vehicle 12 may include a battery 40 operativelyconnected to supply electric power to one or more electric motors 42configured to propel the takeoff assist vehicle 12, the battery 40 maybe disposed between the first and second ground-engaging wheels 34, 36.

The takeoff assist vehicle 12 may include a flywheel 50.

The flywheel 50 may be disposed between the first and secondground-engaging wheels 34, 36.

In some embodiments of the aircraft takeoff assist system 38: the firstground-engaging wheel 34 may be disposed between the vehicle couplingcounterpart 62 and the second ground-engaging wheel 36; and the firstground-engaging wheel 34 may be steerable.

The takeoff assist vehicle 12 may include a steering damper 90associated with the first ground-engaging wheel 34.

The vehicle coupling counterpart 62 may be movably attached to the frame88 of the takeoff assist vehicle 12.

The vehicle coupling counterpart 62 may be attached to a push link 30movably attached to the frame 88 of the takeoff assist vehicle 12.

The takeoff assist vehicle 12 may include a damper (e.g., pad 96)operatively disposed between the push link 30 and the frame 88 of thetakeoff assist vehicle 12.

A position of the second ground-engaging wheel 36 relative to the frame88 of the takeoff assist vehicle 12 may be variable.

Embodiments of the aircraft takeoff assist system 38 may includecombinations of the above features.

In another aspect, the disclosure describes an aircraft assist vehicle12 comprising: a frame 88; ground-engaging wheels 34, 36 mounted to theframe 88; a power source (e.g., vehicle battery 40, vehicle motor 42)for driving one or more of the ground-engaging wheels 34, 36; and avehicle coupling counterpart 62 for engagement with an aircraft couplingcounterpart 64 of an aircraft 10 to define a swivel connection fortransferring a propulsive force from the aircraft assist vehicle 12 tothe aircraft 10, the vehicle coupling counterpart 62 including anupwardly tapered projection 68 having an electric port for transferringelectric power from the aircraft assist vehicle 12 to the aircraft 10.

The projection 68 may have a conical shape.

The projection 68 may have a data port for transferring data between theaircraft assist vehicle 12 and the aircraft 10.

The ground-engaging wheels 34, 36 may consist of a first ground-engagingwheel 34 and a second ground-engaging wheel 36 arranged in tandem.

The vehicle coupling counterpart 62 may be disposed in tandem with thefirst and second ground-engaging wheels 34, 36.

Embodiments of the aircraft assist vehicle 12 may include combinationsof the above features.

In another aspect, the disclosure describes a method 1000 of propellingan aircraft 10 with an assist vehicle 12 during a takeoff roll, themethod 1000 comprising: with the assist vehicle 12 coupled to a landinggear 22 of the aircraft 10 and disposed aft of the landing gear 22,propelling the aircraft 10 with the assist vehicle 12 by transferring apropulsive force from the assist vehicle 12 to the aircraft 10 via thelanding gear 22 during the takeoff roll; and after propelling theaircraft 10 with the assist vehicle 12 during the takeoff roll,decoupling the assist vehicle 12 from the landing gear 22 of theaircraft 10.

The assist vehicle 12 may be an unmanned two-wheeled motorcycle.Decoupling the assist vehicle 12 from the landing gear 22 may includeusing upward movement of the landing gear 22 to automatically disengagethe assist vehicle 12 from the landing gear 22.

The landing gear 22 may be a main landing gear 22 of the aircraft 10.

The assist vehicle 12 may be a first assist vehicle 12A coupled to afirst strut 26A of the main landing gear 22 and the method 1000 mayinclude: with a second assist vehicle 12B coupled to a second strut 26Bof the main landing gear 22 of the aircraft 10 and disposed aft of themain landing gear 22, transferring the propulsive force from the firstand second assist vehicles 12A, 12B to the aircraft 10 via the mainlanding gear 22 during the takeoff roll; and after propelling theaircraft 10 with the first and second assist vehicles 12A, 12B duringthe takeoff roll, decoupling the first and second assist vehicles 12A,12B from the main landing gear 22 of the aircraft 10.

In some embodiments of the method 1000: the aircraft 10 may include oneor more electric aircraft motors 14; and the method 1000 may includepropelling the aircraft 10 with the one or more electric aircraft motors14 when propelling the aircraft 10 with the assist vehicle 12.

The method 1000 may include transferring electric power from the assistvehicle 12 to the one or more electric aircraft motors 14 of theaircraft 10 when propelling the aircraft 10 with the assist vehicle 12.

The method 1000 may include transferring electric power from the assistvehicle 12 to the aircraft 10 when propelling the aircraft 10 with theassist vehicle 12.

The method 1000 may include powering one or more aircraft systems 20using the electric power from the assist vehicle 12 when propelling theaircraft 10 with the assist vehicle 12.

The method 1000 may include: receiving data from the aircraft 10 at theassist vehicle 12 when propelling the aircraft 10 with the assistvehicle 12; and controlling the assist vehicle 12 based on the datareceived from the aircraft 10.

The method 1000 may include causing recuperative braking of the assistvehicle 12 after decoupling the assist vehicle 12 from the landing gear22 of the aircraft 10 to energise a flywheel 50 of the assist vehicle12.

Embodiments of the method 1000 may include combinations of the abovefeatures.

In another aspect, the disclosure describes a method 1000 of propellingan aircraft 10 on ground using a two-wheeled unmanned motorcycle 12, themethod 1000 comprising: coupling the two-wheeled unmanned motorcycle 12to a landing gear 22 of the aircraft 10; and propelling the aircraft 10with the two-wheeled unmanned motorcycle 12 by transferring a propulsiveforce from the two-wheeled unmanned motorcycle 12 to the aircraft 10 viathe landing gear 22 when the aircraft 10 is on ground.

The two-wheeled unmanned motorcycle 12 may be disposed aft of thelanding gear 22 when the aircraft 10 is propelled by the two-wheeledunmanned motorcycle 12.

In some embodiments of the method 1000: the landing gear 22 may be amain landing gear 22 of the aircraft 10; the two-wheeled unmannedmotorcycle 12 may be a first two-wheeled unmanned motorcycle 12A coupledto a first strut 26A of the main landing gear 22; and the method 1000may include, with a second two-wheeled unmanned motorcycle 12B coupledto a second strut 26B of the main landing gear 22 of the aircraft 10,transferring the propulsive force from the first and second two-wheeledunmanned motorcycles 12A, 12B to the aircraft 10 via the main landinggear 22 when the aircraft 10 is on ground.

The method 1000 may include propelling the aircraft 10 with thetwo-wheeled unmanned motorcycle 12 during a takeoff roll of the aircraft10.

The method 1000 may include transferring electric power from thetwo-wheeled unmanned motorcycle 12 to the aircraft 10 when propellingthe aircraft 10 with the two-wheeled unmanned motorcycle 12.

Embodiments of the method 1000 may include combinations of the abovefeatures.

The embodiments described in this document provide non-limiting examplesof possible implementations of the present technology. Upon review ofthe present disclosure, a person of ordinary skill in the art willrecognize that changes may be made to the embodiments described hereinwithout departing from the scope of the present technology. Yet furthermodifications could be implemented by a person of ordinary skill in theart in view of the present disclosure, which modifications would bewithin the scope of the present technology.

1. An aircraft takeoff assist system comprising: an aircraft couplingcounterpart attached to a strut of a landing gear of an aircraft; and atakeoff assist vehicle including: a frame; ground-engaging wheelsmounted to the frame; a power source for driving one or more of theground-engaging wheels; and a vehicle coupling counterpart forengagement with the aircraft coupling counterpart, the aircraft couplingcounterpart and the vehicle coupling counterpart defining a swivelconnection for transferring a propulsive force from the takeoff assistvehicle to the aircraft, the aircraft coupling counterpart beingdisengageable from the vehicle coupling counterpart by upward movementof the aircraft coupling counterpart relative to the vehicle couplingcounterpart.
 2. The aircraft takeoff assist system as defined in claim1, wherein the takeoff assist vehicle is an unmanned two-wheeledmotorcycle.
 3. The aircraft takeoff assist system as defined in claim 1,wherein the swivel connection is disposed aft of the strut of thelanding gear.
 4. The aircraft takeoff assist system as defined in claim3, wherein the landing gear is a main landing gear of the aircraft. 5.The aircraft takeoff assist system as defined in claim 1, wherein: thetakeoff assist vehicle is a first takeoff assist vehicle; the aircraftcoupling counterpart is a first aircraft coupling counterpart; the strutis a first strut; the landing gear is a main landing gear of theaircraft; and the aircraft takeoff assist system includes a secondtakeoff assist vehicle for engagement with a second strut of the mainlanding gear.
 6. The aircraft takeoff assist system as defined in claim5, wherein the first and second takeoff assist vehicles are unmannedtwo-wheeled motorcycles.
 7. The aircraft takeoff assist system asdefined in claim 1, wherein: the aircraft coupling counterpart includesa socket with a downwardly facing opening; and the vehicle couplingcounterpart includes a projection configured to be received in thesocket.
 8. The aircraft takeoff assist system as defined in claim 7,wherein the projection is upwardly tapered.
 9. The aircraft takeoffassist system as defined in claim 7, wherein the projection has aconical shape.
 10. The aircraft takeoff assist system as defined inclaim 7, wherein the projection and the socket cooperatively define anelectric power transfer interface between the takeoff assist vehicle andthe aircraft.
 11. The aircraft takeoff assist system as defined in claim7, wherein the projection and the socket cooperatively define a datatransfer interface between the takeoff assist vehicle and the aircraft.12. The aircraft takeoff assist system as defined in claim 1, whereinthe aircraft coupling counterpart is disposed aft of the strut and isattached to the strut via a trailing link.
 13. The aircraft takeoffassist system as defined in claim 1, wherein: the takeoff assist vehicleis an unmanned two-wheeled vehicle having a first ground-engaging wheeland a second ground-engaging wheel arranged in tandem; and the vehiclecoupling counterpart is disposed in tandem with the first and secondground-engaging wheels of the takeoff assist vehicle.
 14. The aircrafttakeoff assist system as defined in claim 13, wherein: the firstground-engaging wheel is disposed between the vehicle couplingcounterpart and the second ground-engaging wheel; and the takeoff assistvehicle includes an electric motor operatively connected to drive thefirst ground-engaging wheel.
 15. The aircraft takeoff assist system asdefined in claim 13, wherein the takeoff assist vehicle includes abattery operatively connected to supply electric power to one or moreelectric motors configured to propel the takeoff assist vehicle, thebattery being disposed between the first and second ground-engagingwheels.
 16. The aircraft takeoff assist system as defined in claim 13,wherein the takeoff assist vehicle includes a flywheel.
 17. The aircrafttakeoff assist system as defined in claim 16, wherein the flywheel isdisposed between the first and second ground-engaging wheels.
 18. Theaircraft takeoff assist system as defined in claim 13, wherein: thefirst ground-engaging wheel is disposed between the vehicle couplingcounterpart and the second ground-engaging wheel; and the firstground-engaging wheel is steerable.
 19. The aircraft takeoff assistsystem as defined in claim 18, wherein the takeoff assist vehicleincludes a steering damper associated with the first ground-engagingwheel.
 20. The aircraft takeoff assist system as defined in claim 18,wherein the vehicle coupling counterpart is movably attached to theframe of the takeoff assist vehicle. 21.-44. (canceled)